EP3568343B1

EP3568343B1 - Adaptive system for controlling a pedal-assisted bicycle and respective method for driving an electric motor of a bicycle

Info

Publication number: EP3568343B1
Application number: EP18704297.3A
Authority: EP
Inventors: Daniele Berretta; Paolo LISANTI; Marcello Segato; Matteo Corno; Sergio Matteo Savaresi
Original assignee: Zehus SpA
Current assignee: Zehus SpA
Priority date: 2017-01-13
Filing date: 2018-01-12
Publication date: 2020-03-11
Anticipated expiration: 2038-01-12
Also published as: CN110191843A; IT201700003184A1; CN110191843B; WO2018130982A1; EP3568343A1

Description

Technical field of the invention

The present invention concerns the field of pedal-assisted bicycles, that is a particular type of bicycle equipped with an electric motor that is suitable for supplying additional power with respect to that provided by the cyclist.
The present invention finds particular, but not exclusive application in the field of the so-called "all-in-the-wheel" pedal-assisted bicycles, that is bicycles in which the motor, batteries, sensors and electronic controls are inserted in a single housing associated with a wheel of the bicycle.
In particular, the present invention concerns a system for controlling an adaptive type of pedal-assisted bicycle, that is a pedal-assisted bicycle that is capable of modifying the control logic thereof as a function of current conditions.

Prior art

EP3009295 discloses the preamble of claim 1.
Various control algorithms are known in the field of pedal-assisted bicycles and they principally differ in the aims they intend to achieve. For example, some algorithms prioritize the comfort of the cyclist over battery duration, whereas others aim instead at increasing the autonomy per charge, a result that is essentially achieved by means of regenerative braking by the motor, which in these circumstances operates as a generator that recharges the battery, thus increasing the effort required of the cyclist in some stages of motion.
Also proposed are algorithms that are such that the batteries of pedal-assisted bicycles in principle never need to be recharged by an external source and that thus use the pedal power provided by the cyclist to ensure an ideally infinite charge.
An algorithm of this type is disclosed for example in patent WO 2013/124764 A1 ; in addition to regeneration during downhill travel and braking, to recharge the battery, this algorithm uses the pedalling of the cyclist, whose effort is modified based on the resisting forces acting upon the bicycle so that part of the pedal power exerted is used to recharge the batteries.
However, although it is efficient in terms of the duration of the battery, this algorithm does not ensure adequate comfort for the cyclist.

Summary of the invention

The issue underlying the present invention is thus that of providing a system for controlling a pedal-assisted bicycle which allows to maintain the battery charge without the aid of external sources and which reduces the overall effort of the cyclist compared to a conventional bicycle.
This and others aims are achieved by an adaptive control system for controlling a pedal-assisted bicycle according to claim 1.
The control system according to the invention optimizes the synergy between the cyclist and the behaviour of an electric bicycle equipped with the control system.
Moreover, the control system according to the invention does not require the presence of a pedal torque sensor for its operation.
Dependent claims 2 to 8 define possible advantageous embodiments of the invention.
It is also an object of the present invention a pedal-assisted bicycle as defined in the enclosed claim 9.
It is also an object of the present invention a method for driving an electric motor of an electrically pedal-assisted bicycle by means of a rechargeable battery as defined in the enclosed claim 10 and in the preferred embodiments disclosed in the dependent claims 11 to 14.
The method for driving the electric motor comprises the steps of:

a1) calculating the value of an inversion speed as a function of a state of charge of a battery, said inversion speed indicating the bicycle speed beneath which the electric motor operates as a motor to supply assistance to the pedal-thrust and above which the motor operates as a generator when the moving bicycle is in a traction condition in which the speed of a wheel of the bicycle is substantially equal to the speed of a free-wheel mechanism associated with a wheel;
a2) calculating, as a function of the battery state of charge, a minimum value corresponding to the maximum energy recovery when the pedal-thrust group has no traction and when the bicycle is not braking;
b) calculating, for a plurality of first states associated with the bicycle during its movement, a plurality of trends of a first portion of a motor nominal command signal, as a function of the calculated values of the inversion speed and of the minimum value;
c1) identifying, as a function of the value of an angular speed of the wheel and of an angular speed of the free-wheel mechanism, the first current state associated with the bicycle during its movement; c2) selecting, out of the plurality of trends of the first portion of the motor nominal command signal, the current trend of the first portion associated with the identified first current state;
c3) calculating, for the selected trend in the first portion, the current value of the first portion of the motor nominal command signal, as a function of the current value of the bicycle speed;
d) calculating the current value of a motor corrected command signal as a function of the first portion and of the state of charge of the battery;
e) driving the electric motor using the calculated current value of the motor corrected command signal;
f) further repeating steps a1), a2), b), c1), c2), c3), d), e).

Preferably, in step a1) of the driving method, the inversion speed is calculated by scaling the inversion speed value with a first coefficient that depends on the state of charge of the battery, wherein said first coefficient is equal to one for values of the state of charge that are greater than a threshold value and decreases towards a minimum value as the state of charge decreases until it reaches the minimum value for small and null values of the state of charge; moreover, in step a2) the minimum value is calculated by scaling the minimum value with a second coefficient that depends on the state of charge of the battery, wherein said second coefficient is equal to a minimum value for values of the state of charge that are greater than the threshold value and increases towards the value of one upon the decrease in the state of charge until it reaches the value of one for small and null values of the state of charge.
Preferably, in step b) of the driving method said plurality of first states comprises at least two of the following states:

▪ Boost: it corresponds to a standing start or abrupt acceleration during the movement phase of the bicycle;
▪ No traction: it corresponds to a condition in which, when the bicycle is moving, the speed of the free-wheel mechanism is lower than the speed of the wheel;
▪ Traction: it corresponds to a condition in which the speed of the free-wheel mechanism is substantially equal to the speed of the bicycle wheel;
▪ Braking: it corresponds to a braking condition.

Preferably, step c1) of the driving method comprises identifying the Traction state and step c2) comprises selecting the trend of a first portion associated with the Traction state, said trend comprising:

▪ a first portion comprised between a null value of the speed of the bicycle and a defined value, wherein the first portion of the motor nominal command signal gradually increases from the null value to a maximum value;
▪ a second portion comprised between said defined value of the speed of the bicycle and the inversion speed value, wherein the second portion of the motor nominal command signal gradually decreases until it reaches the null value;
▪ a third portion comprised between the inversion speed value and a maximum speed value, wherein the third portion of the motor nominal command signal is negative until it reaches said minimum value;
▪ a fourth portion greater than the maximum speed value, wherein the fourth portion of the motor nominal command signal is substantially equal to said minimum value.

Preferably, in step d) of the driving method the current value of the motor corrected command signal is calculated:

in case wherein the value of the first portion of the motor nominal command signal is positive, by scaling the first portion of the motor nominal command signal with a third coefficient that depends on the state of charge of the battery, wherein the third coefficient is equal to one for values of the state of charge that are greater than the threshold value, whereas it decreases towards the null value for values lower than the threshold value until it becomes null for small and null values of the state of charge;
in case wherein the value of the first portion of the motor nominal command signal is negative, by scaling the first portion of the motor nominal command signal with a fourth coefficient that depends on the battery state of charge, wherein the fourth coefficient is equal to one for values of the state of charge that are lower than the threshold value, whereas it decreases towards the null value for values greater than the threshold value until it reaches the null value at the full charge value.

It is also an object of the present invention a computer program as defined in the enclosed claim 15.
It is also an object of the present invention a non-transitory computer-readable medium having a program recorded thereon, said medium comprising software code adapted to perform the steps of the method for driving the electric motor of an electrically pedal-assisted bicycle, when said program is run on at least one computer.

Brief description of the drawings

For a better understanding of the invention and for appreciating the advantages thereof, several non-limiting example embodiments shall be described herein below, referring to the attached figures, of which:

Figure 1 is a schematic illustration of a pedal-assisted bicycle;
Figure 2 is a block diagram of an adaptive system for controlling a pedal-assisted bicycle according to a possible embodiment of the invention;
Figure 3 is a block diagram of a nominal control module of the adaptive system for controlling a pedal-assisted bicycle according to a possible embodiment of the invention;
Figures 4a-4f are diagrams showing possible trends of a motor nominal command signal of a pedal-assisted bicycle, said trends being supplied by the adaptive control system according to a possible embodiment of the invention;
Figure 5 is a block diagram of an adaptive control module of the adaptive system for controlling a pedal-assisted bicycle according to a possible embodiment of the invention;
Figures 6a-6b are diagrams showing possible trends of correction coefficients as determined by the adaptive control module of the adaptive system according to a possible embodiment of the invention;
Figures 7a-7b are diagrams showing possible trends of further correction coefficients as determined by the adaptive control module of the adaptive system according to a possible embodiment of the invention;
Figures 8a-8c show the flow diagram of a method for driving an electric motor of an electrically pedal-assisted bicycle.

Detailed description of the invention

Figure 1 schematically shows a pedal-assisted bicycle 100.
The bicycle 100 comprises an electric motor 101 associated with one wheel 102 of the bicycle wheels, that is, the front or preferably the rear wheel.
The bicycle 100 further comprises a pedal-thrust group 103, by means of which the cyclist can supply power to the bicycle, and it is connected to one of the wheels, preferably the same wheel 102 with which the motor 101 is associated, by means of a transmission 104, for example a chain drive transmission.
The transmission 104 comprises a free-wheel mechanism 105 which makes it possible to decouple the wheel 102 and the pedal-thrust group 103 in the case in which, under conditions of advancement, the angular speed of the wheel 102 is greater than that of the pedal-thrust group 103 or of the pinion associated with the wheel 102 in the case in which it is provided between the pedal-thrust group 103 and the wheel.
For example, the free-wheel mechanism 105 enables backward movement of the pedal-thrust group 103 or possibly the stopping of pedalling without the latter interfering with the advancement movement of the wheel and thus of the bicycle itself during motion thereof.
The bicycle 100 further comprises a rechargeable battery 106 connected to the electric motor 101 in such a manner as to be able to exchange energy with the motor. The battery 106 can be made up of one or more cells connected in series.
In particular, the battery 106 can be recharged by the electric motor 101, when the motor operates as a generator (energy recovery condition), and it can supply energy to the electric motor 101 when the motor supplies assistance to the pedal-thrust (interlocked condition), that is when it operates a motor.
The battery 106 can be separated from the motor 101 or, in accordance with an alternative configuration of the "all-in-one" type, it can be housed inside a common closure body solidly connected to the wheel 102 together with the electric motor 101.
With reference to Figure 2, the bicycle 100 comprises a control system 1 of the adaptive type, which commands the electric motor 101 so as to assist the cyclist in assisted pedalling.
In particular, the control system 1 is configured to generate a motor reference command signal I°_ref (in particular, a current signal) upon which the driving or resisting torque of the motor depends.
The control system 1 comprises a nominal control module 2 (that is, a nominal controller) configured to output a motor nominal command signal I°_motor (in particular, a current signal).
The nominal control module 2 is implemented for example by means of sequential and combinational logic realized with VHDL or Verilog code and synthesized in a programmable logic device (for example an FPGA) .
Alternatively, the nominal control module 2 is implemented with software code portions (using for example the "C" language) executed in a processing unit (for example, a microprocessor).
The nominal control module 2 determines the motor nominal command signal I°_motor based on inputs coming from sensors associated with the control system 1 and/or the bicycle 100.
In particular, the system 1 comprises a sensor for detecting the angular speed ω_wheel of the wheel 102 and it is configured to generate a signal representative of the angular speed ω_wheel of the wheel 102. The system 1 further comprises a sensor for detecting the angular speed ω_free-wheel of the free-wheel mechanism 105 associated with the wheel 102 and it is configured to generate a signal representative of the angular speed ω_free-wheel of the free-wheel mechanism 105.
Additionally, the system 1 can comprise a sensor for measuring the slope ϑ̃ (that is, the inclination) of the route along which the bicycle 100 is moving, wherein the sensor is configured to generate a signal representative of the measured slope ϑ̃; alternatively, the system 1 comprises a module for estimating slope ϑ̃ (that is, an estimator of slope ϑ̃) and it is configured to generate a signal representative of the estimated slope ϑ̃.
In the case in which the slope ϑ̃ is not directly measured, but it is estimated, this estimate can be made by employing additional sensors (for example, inertial measurement units) and specific estimation algorithms (by way of example, see: 1) Ivo Boniolo, Stefano Corbetta, Sergio Savaresi. Attitude estimation of a motorcycle in a Kalman filtering framework. In Advances in Automotive Control, pages 779-784, 2010. 2) Sergio Savaresi, Ivo Boniolo. Estimate of the lean angle of motorcycles. VDM Verlag, 2010).
The motor nominal command signal I°_motor represents the motor control signal that is ideal for ensuring adequate comfort for the cyclist owing to the assistance provided by the motor 101.
As shall be seen below, this motor nominal command signal I°_motor is modified, with the procedures that shall be described, so as to obtain the motor reference command signal I°_ref, which takes into account the need to maintain the battery charge 106 without having to connect it to external sources of energy.
The control system 1 further comprises an adaptive control module 3 (that is, an adaptive controller 3) that is configured to generate a motor corrected command signal I°_motor,corr (in particular, a current signal) which is determined starting from the motor nominal command signal I°_motor which is corrected based on the state of charge SoC (that is, the charge level) of the battery 106. For this purpose, the system 1 comprises a sensor (for example, an electronic circuit) for detecting the state of charge SoC of the battery 106 and it is configured to generate a signal representative of the state of charge SoC of the battery 106.
The adaptive control module 3 is implemented for example by means of sequential and combinational logic realized with VHDL or Verilog code and synthesized in a programmable logic device (for example an FPGA) .
Alternatively, the adaptive control module 3 is implemented with software code portions (using for example the "C" language) executed in a processing unit (for example, a microprocessor).
According to a possible embodiment, the system 1 comprises one or more saturation modules 8', 8", 8''' for saturating the motor corrected command signal I°_motor,corr and which are configured to generate a motor limit command signal I°_motor,lim (in particular a current signal) which is obtained starting from the motor corrected command signal I°_motor,corr reduced by one or more coefficients η, ϑ, σ comprised between 0 and 1 based on detected operating parameters of the electric motor 101 and/or of the battery 106.
These modules 8', 8", 8" substantially have the function of preserving the components of the system.
According to a possible embodiment, a first saturation module 8' is configured to modify the motor corrected command signal I°_motor,corr by means of the coefficient η, which is comprised between 0 and 1, in such a manner that the voltage drop across the battery 106 is kept within the allowable maximum Vcell_max and minimum Vcell_min limits. Therefore, for the purpose of preventing damage to the battery 106, the first saturation module 8' operates in such a manner that the voltage drop across the battery 106 does not fall below the minimum value Vcell_min during the motor interlock step and does not exceed the maximum value Vcell_max during the recharging step.
According to a possible embodiment, a second saturation module 8" is configured to modify the motor corrected command signal I°_motor,corr when the signal is negative, by means of the coefficient ϑ, which is comprised between 0 and 1, in such a manner as to reduce recovery, that is, in such a manner as to increase (that is, make less negative) the motor corrected command signal I°_motor,corr at low bicycle speeds, given that under such conditions the motor is less efficient and tends to operate as an active brake and not as a regenerative brake.
For example, the bicycle speed v can be determined starting from the signal representative of the angular speed ω_wheel of the wheel 102 by means of the relation v = ω_wheel R, in which R is the radius of the wheel 102.
According to a possible embodiment, a third saturation module 8''' is configured to modify the motor corrected command signal I°_motor,corr when the signal is positive, by means of the coefficient σ, which is comprised between 0 and 1, in such a manner as to reduce the interlock upon the increase in the temperature of the motor. This prevents the temperature from exceeding the allowable limits, which would result in possible damage to the motor.
For this purpose, the system 1 advantageously comprises a sensor configured to detect the temperature T of the motor 101 and to generate a signal representative of the temperature T.
According to a possible embodiment, the system 1 comprises a filter 4 (preferably a low-pass filter) having the function of filtering the motor limit command signal I°_motor,lim and outputting a motor filtered command signal I°_motor,filtr (in particular a current signal).
The motor reference command signal I°_ref , according to this embodiment, corresponds to the motor filtered command signal I°_motor,filtr.
Note that in the case in which the saturation modules 8', 8", 8''' are not present, the motor limit command signal I°_motor,lim coincides with the motor corrected command signal I°_motor,corr which is filtered by the filter 4.
Note also that, likewise, in the case in which the filter 4 is not present either, the motor reference command signal I°_ref corresponds to the motor corrected command I°_motor,corr.
According to a possible embodiment, the system 1 comprises a failure detecting module 5 (that is, a failure sensor) configured to deactivate the motor 101 or to modulate the motor reference command signal I°_ref in the presence of detected failures in the system 1.
The nominal control module 2 and the adaptive control module 3 shall now be described in detail.
With reference to Figure 3, a block diagram of the nominal control module 2 is shown according to a possible embodiment of the invention.
The nominal control module 2 comprises a first finite state machine 6 and preferably a second finite state machine 7.
The first finite state machine 6 is configured to generate a first portion i°_cyclist of the motor nominal command signal I°_motor and the second finite state machine 7 is configured to generate a second portion i°_slope of the motor nominal command signal I°_motor, such that the latter is given by the sum of the first portion i°_cyclist and the second portion i°_slope of the motor nominal command signal I°_motor.
For example, the first portion i°_cyclist and the second portion i°_slope are signals of current.
Referring to the first finite state machine 6, the machine 6 is configured to generate the first portion i°_cyclist of the motor nominal command signal I°_motor based on a state determined on the basis of the signal representative of the angular speed of the wheel ω_wheel and on the basis of the signal representative of the angular speed ω_free-wheel and possibly on the basis of an additional signal representative of the braking state ("braking").
With reference to the latter, note that, according to a possible embodiment, the bicycle can comprise a mechanical brake that can be activated with a handle, the activation of which is translated into said signal representative of the braking state.
Alternatively, or additionally, the bicycle may not have mechanical brakes and the braking action can be ensured by the electric motor 101 acting as a generator, which generates a resisting torque such as to brake the bicycle. The braking action in this case can be activated by pedalling backwards on the pedal-thrust group. This situation can be detected on the basis of the signal representative of the angular speed of the wheel ω_wheel and the signal representative of the angular speed ω_free-wheel, which will be positive and negative, respectively, in the case of pedalling backwards while the bicycle is in motion.
For example, the first finite state machine 6 can be configured to detect the following states:

BOOST: corresponding to a standing start or abrupt acceleration during the movement phase of the bicycle. This state is preferably of finite duration, which can be established for example as a function of the number of pedal revolutions, or it can last until the bicycle reaches a predefined speed.
NO TRACTION: corresponding to a condition in which, with the bicycle moving, the speed of the free-wheel mechanism is lower than the speed of the wheel. For example, this condition occurs when the bicycle is moving downhill without pedalling;
TRACTION: corresponding to a condition in which the speed of the free-wheel mechanism, minus a tolerance, is equal to the speed of the bicycle wheel; this state corresponds for example to a condition of cruising at an approximately constant bicycle speed while pedalling;
BRAKING: corresponding to a condition of braking the bicycle, according to said procedures.

Figure 3 reports possible criteria according to which the first finite state machine 6 passes from one state to another, assuming that starting from the condition in which the bicycle is stopped and in the absence of pedalling (ω_wheel = 0 and ω_free-wheel = 0), upon starting, the machine is brought into the "BOOST" state.
Note that in Figure 3, k indicates a predefined constant and φped_start indicates the angle of rotation of the pedal-thrust group 103 upon starting, and which can be determined directly by means of a specific sensor or indirectly for example starting from the signal representative of the angular speed of the free-wheel mechanism ω_free-wheel.
The terms "ON" and "OFF" associated with braking indicate the conditions of active braking and no braking, respectively.
In particular:

the machine passes from the "Boost" state into the "No Traction" state when the absolute value of the difference between the value of the angular speed of the wheel ω_wheel and the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 is lower than the value of the constant k, and additionally the brake on the bicycle 100 is not activated, that is, the condition (|ω_wheel-ω_free-wheel| <k) AND brake=OFF) is respected;
the machine passes from the "Boost" state into the "Traction" state when the absolute value of the difference between the value of the angular speed of the wheel ω_wheel and the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 is lower than the value of the constant k, and additionally the value of the angle of rotation φped_start is greater than 2n, that is, the condition (|ω_wheel-ω_free-wheel| <k AND φped_start>2π) is respected. In other words, the condition concerning the pedal position is used in the standing start to determine when to pass from the "Boost" state to the "Traction" state, supplying assistance to the pedal-thrust if the condition concerning the angular speed is met; then after one rotation of the pedals, the machine passes into the "Traction" state;
the machine passes from the "Boost" state into the "Braking" state when the brake on the bicycle 100 is activated and additionally the value of the angular speed of the wheel ω_wheel is greater than 0, that is, the condition (brake=ON AND (ω_wheel>0)) is respected;
the machine remains in the "Boost" state as long as the absolute value of the difference between the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 and the value of the angular speed of the wheel ω_wheel is greater than or equal to the value of the constant k, that is, the condition (|ω_free-wheel-ω_wheel|≥ k) is respected;
from the "No Traction" state, the machine returns to the "Boost" state when the value of the angular speed of the wheel ω_wheel is less than or equal to 0 and in addition, the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 is equal to 0, that is, the condition (ω_wheel≤0 AND ω_free-wheel=0) is respected;
the machine passes from the "No Traction" state into the "Traction" state when the absolute value of the difference between the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 and the value of the angular speed of the wheel ω_wheel is lower than the value of the constant k, that is, the condition (|ω_free-wheel-ω_wheel| <k) is respected;
the machine passes from the "No Traction" state into the "Braking" state when the brake on the bicycle 100 is activated and additionally the value of the angular speed of the wheel ω_wheel is greater than 0, that is, the condition (brake=ON AND (ω_wheel>0)) is respected;
the machine remains in the "No Traction" state as long as the absolute value of the difference between the value of the angular speed of the wheel ω_wheel and the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 is greater than or equal to the value of the constant k, and additionally the brake on the bicycle 100 is not activated, that is, the condition (|ω_wheel-ω_free-wheel|≥k) AND brake=OFF) is respected;
the machine passes from the "Traction" state into the "Boost" state when the value of the angular speed of the wheel ω_wheel is less than or equal to 0 and in addition, the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 is less than or equal to 0, that is, the condition (ω_wheel≤0 AND ω_free-wheel≤0) is respected;
the machine passes from the "Traction" state into the "No Traction" state when the absolute value of the difference between the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 and the value of the angular speed of the wheel ω_wheel is greater than the value of the constant k, and additionally the brake on the bicycle 100 is not activated, that is, the condition (|ω_free-wheel-ω_wheel|>k) AND brake=OFF) is respected;
the machine passes from the "Traction" state into the "Braking" state when the brake on the bicycle 100 is activated and additionally the value of the angular speed of the wheel ω_wheel is greater than 0, that is, the condition (brake=ON AND (ω_wheel>0)) is respected;
the machine remains in the "Traction" state as long as the value of the angular speed of the wheel ω_wheel is greater than 0 or the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 is greater than 0, and additionally the absolute value of the difference between the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 and the value of the angular speed of the wheel ω_wheel is lower than or equal to the value of the constant k and in addition the brake on the bicycle 100 has not been activated, that is, the condition (ω_wheel>0 OR ω_free-wheel>0) AND (|ω_free-wheel-ω_wheel|≥k) AND brake=OFF is respected;
the machine passes from the "Braking" state into the "Boost" state when the value of the angular speed of the wheel ω_wheel is less than or equal to 0 and additionally the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 is less than or equal to 0, and in addition, the brake on the bicycle 100 has not been activated, that is, the condition (ω_wheel≤0 AND ω_free-wheel≤0 AND BRAKE=OFF) is respected;
the machine passes from the "Braking" state into the "Traction" state when the brake on the bicycle 100 is not activated and additionally the absolute value of the difference between the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 and the value of the angular speed of the wheel ω_wheel is lower than the value of the constant k, that is, the condition (brake=OFF AND (|ω_free-wheel-ω_wheel|<k)) is respected;
the machine passes from the "Braking" state into the "No Traction" state when the brake on the bicycle 100 is not activated and additionally the absolute value of the difference between the value of the angular speed ω_free-wheel of the free-wheel mechanism 105 and the value of the angular speed of the wheel ω_wheel is greater than the value of the constant k, that is, the condition (brake=OFF AND (|ω_free-wheel-ω_wheel|>k)) is respected;

Figures 4a-4d shows possible trends of the first portion i°_cyclist of the motor nominal command signal I°_motor in the different states of the first finite state machine 6.
In the "BOOST" state (Figure 4a), starting from zero, the signal i°_cyclist gradually reaches, for example linearly, a maximum value i_boost,max when the angle of rotation of the pedal-thrust group Φ_{ped start} reaches a predefined value φ_{boost max}, which is preferably less than 2n, that is, before the pedal-thrust group 103 has performed a complete revolution.
In the "TRACTION" state (Figure 4b), when the speed of the bicycle v (which can be determined by means of the relation v = ω_wheel*R, in which R is the radius of the wheel 102) is comprised between zero and a predetermined value v_curr,max, the signal i°_cyclist, starting from zero, gradually reaches, for example linearly, a maximum value i_boost,max.
Between the speed value v_curr,max and the inversion speed value v_limit, the signal i°_cyclist decreases gradually, for example linearly, remaining positive until it reaches the null value. Upon the increase in the speed of the bicycle v beyond the inversion speed value v_limit, the signal i°_cyclist becomes negative until it reaches a minimum value i_rec,min, corresponding to a maximum energy recovery condition, at a maximum speed v_rech,max.
The above illustrates the fact that assistance by the motor is greater at low speeds, decreases with increasing speeds until it becomes null at the inversion speed v_limit. When the latter speed is exceeded, the motor starts to operate as a generator, that is, it no longer provides added torque, but it forces the cyclist to provide added power, which serves to recharge the battery 106.
Note that the maximum effort is required of the cyclist at the speed v_rech,max, which is preferably selected so as to correspond to a pedalling cadence of about 70 revolutions/min, at which it has been verified that maximum efficiency is attained by the cyclist.
In the "BRAKING" (Figure 4c) and "NO TRACTION" (Figure 4d) states, starting from zero, the signal i°_cyclist decreases gradually, for example linearly, starting from a minimum speed for activation of the recovery v_gen,min from zero, until it reaches the minimum value, i_brake,min and i_rec,min, respectively, at a maximum speed v_gen,max.
For speeds higher than this maximum speed v_gen,max, the signal i°_cyclist remains constant and equal to i_brake,min and i_rec,min, respectively.
Note that the value i_rec,min corresponds to the maximum energy recovery when the pedal-thrust group has no traction and when the bicycle is not braking.
The value of i_rec,min is selected so as not to excessively influence the perception on the part of the cyclist when the cyclist is pedalling in this condition.
Referring now to be second finite state machine 7, it can be configured to detect the following states:

"DOWN-HILL": This state corresponds to a condition in which the bicycle is moving along a downhill route;
"FLAT": This state corresponds to a condition in which the bicycle is moving along a substantially flat route;
"UP-HILL": This state corresponds to a condition in which the bicycle is moving along an uphill route.

Figure 3 shows possible criteria according to which the second finite state machine 7 passes from one state to another.
Note that in Figure 3, h and c indicate predefined constants and ϑ̃ indicates the measured or estimated slope.
The constants h and c are selected so as to obtain operation with hysteresis:

when the slope ϑ̃ fluctuates around the null value (that is, in the "FLAT" state), the second finite state machine waits until the slope ϑ̃ exceeds the absolute value of the sum of h and c in order to change states, that is, the condition (ϑ̃≤|h+c|) is respected;
in the "DOWNHILL" and "UPHILL" states, the machine waits until the slope ϑ̃ is lower than the absolute value of the difference between h and c, before returning to the "FLAT" state, that is, it remains in the "DOWNHILL" and "UPHILL" states as long as the condition (ϑ̃ ≥ |h-c|) is respected.

In this manner, the change in states is carried out only when it is certain that the slope ϑ̃ is consistent with the situation in which bicycle control system is actually found.
In particular:

the machine passes from the "DOWNHILL" state into the "FLAT" state when the value of the slope ϑ̃ is greater than the value (-h+c), that is, the condition (ϑ̃ >-h+c) is respected;
the machine remains in the "DOWNHILL" state as long as the value of the slope ϑ̃ is greater than or equal to the absolute value of the difference between h and c, that is, the condition (ϑ̃ ≥|h-c|) is respected;
from the "FLAT" state, the machine returns to the "DOWNHILL" state when the value of the slope ϑ̃ is lower than the value (-h-c), that is, the condition (ϑ̃ <-h-c) is respected;
the machine passes from the "FLAT" state into the "UPHILL" state when the value of the slope ϑ̃ is greater than the value(+h+c), that is, when the condition (ϑ̃ >+h+c) is respected;
the machine remains in the "FLAT" state as long as the value of the slope ϑ̃ is lower than or equal to the absolute value of the sum of h and c, that is, the condition ϑ̃≤|h+c| is respected;
from the "UPHILL" state, the machine returns to the "FLAT" state when the value of the slope ϑ̃ is lower than the value (+h+c), that is, the condition (ϑ̃ <+h+c) is respected;
the machine remains in the "UPHILL" state as long as the value of the slope ϑ̃ is greater than or equal to the absolute value of the difference between h and c, that is, the condition (ϑ̃ ≥|h-c|) is respected;

Figures 4e-4f report possible trends of the second portion i°_slope of the motor nominal command signal I°_motor in the different states of the second finite state machine 7.
In the "FLAT" state, the contribution of the second finite state machine 7 to the motor nominal command signal I°_motor is null.
In the "UPHILL" state (Figure 4e), the signal i°_slope increases gradually, for example linearly, starting from zero, upon the increase in the estimated or measured slope ϑ̃, until it reaches a maximum value i_max. Therefore, assistance by the motor increases with the increase in slope.
In the "DOWNHILL" state /Figure 4f), the signal i°_slope decreases gradually, for example linearly, starting from zero, upon the decrease in the estimated or measured slope ϑ̃ (that is, with the increase in the slope of the descent), until it reaches a minimum value, or maximum in terms of absolute value i_min. Therefore, recovery by the motor increases with the increase in the slope of the descent, up to a maximum recovery value.
Referring now to Figure 5, a block diagram of the adaptive control module 3 is shown according to a possible embodiment of the invention.
The adaptive control module 3 comprises a correction module for correcting the nominal command signal 9 (that is, a command corrector) and a correction module 10 for correcting the parameters (that is, a parameter corrector) of the nominal control module 2, particularly of the first finite state machine 6.
With reference to the correction module 9 for correcting the nominal command signal, this module receives as an input the motor nominal command signal I°_motor and a signal representative of the state of charge SoC of the battery 106 and scales by a coefficient µ⁺ or by a coefficient µ^- the motor nominal command signal I°_motor depending on whether the latter is positive or negative, respectively, as a function of the state of charge SoC.
The coefficients µ⁺ and µ^- can vary as a function of the state of charge SoC based on predefined laws and possible trends thereof are shown in Figures 6a and 6b.
In particular, the coefficient µ⁺ (Figure 6a) is equal to 1 for charge values exceeding a threshold value SoC° and it decreases upon the decrease in the charge until it becomes null for small and null values of the charge.
The coefficient µ^- (Figure 6b) is equal to 1 for charge values below a threshold value SoC° and it decreases upon the increase in the charge until it reaches a null value at the full charge value.
In this manner, the interlock is limited in the case of a low level of the battery 106, whereas recharging is limited in the case of a high charge level of the battery 106.
Returning back to Figure 5, the correction module 10 for correcting the parameters of the nominal control module 2 receives as an input the signal representative of the state of charge SoC of the battery 106 and it scales the inversion speed v_limit and the minimum value i_rec,min of the signal i°_cyclist, by a coefficient χ and by a coefficient ξ respectively.
The coefficients χ and ξ can vary as a function of the state of charge SoC based on predefined laws and possible trends thereof are shown in Figures 7a and 7b.
In particular, the coefficient χ (Figure 7a) is equal to 1 for charge values exceeding the threshold value SoC° and it decreases upon the decrease in the charge until it reaches a minimum constant value for small and null values of the charge.
The coefficient ξ (Figure 7b) is equal to 1 for charge values below the threshold value SoC° and it decreases upon the increase in the charge until it reaches a minimum constant value for almost full or full charge values.
In this manner, for low charge values, the inversion speed v_limit is reduced, and therefore energy recovery in the "TRACTION" state takes place starting from low speeds of the bicycle and additionally assistance to the pedal-thrust also takes place only for low speeds, on the whole thereby facilitating the recharging process.
Moreover, under these conditions, there is maximum energy recovery, given that the value i_rec,min of the signal i°_cyclist is a minimum value, or maximum in terms of absolute value.
Conversely, for high charge values, the inversion speed v_limit remains at the nominal value, and therefore energy recovery in the "TRACTION" state takes place starting from the higher bicycle speeds and additionally, assistance takes place over a wider range of speeds, thus prioritizing the interlock over the battery charge.
Moreover, under these conditions, there is minimum recovery according to that which is provided for by the nominal logic, as the value i_rec,min of the signal i°_cyclist is a maximum value (that is, it is less negative).
Note that in this description and in the appended claims, the adaptive control system 1, as well as the elements indicated by the term "module", can be implemented by means of hardware devices (e.g. control units), by means of software or by means of a combination of hardware and software.
For the purpose of meeting contingent and specific needs, a person skilled in the art can introduce numerous additions, modifications or replacements of elements with other functionally equivalent elements in the disclosed embodiments of the system for adaptive control of a pedal-assisted bicycle, without, however, deviating from the scope of the appended claims.
Figures 8a-c show a flow diagram of a method 200 for driving the electric motor 101 of the electrically pedal-assisted bicycle.
The electric motor 101 is such to have a first and a second operating mode.
In the first operating mode (previously indicated as the "interlocked condition"), the electric motor is such to operate as a motor supplied by the battery 106, that is, it is such to convert the electric power supplied by the battery 106 into mechanical power used to set the electric motor into rotation and thus contribute to the movement of the bicycle, supplying the cyclist with assistance to the pedal-thrust.
In the second operating mode (previously indicated as the "energy recovery condition"), the electric motor is such to operate as an electric generator in order to charge the battery 106.
The driving method 200 begins with step 201 and comprises steps 202-214, which are repeated cyclically, for example with a period of 10 milliseconds.
A first operating cycle, in which steps 202-214 are performed, is illustrated herein below.
Step 201 is followed by step 202, in which the inversion speed value v_limit is calculated as a function of the state of charge SoC of the battery 106.
In particular, in step 202, the nominal value of the inversion speed v_limit is scaled (that is, multiplied) by a coefficient χ having values comprised between 0 and 1 as a function of the state of charge SoC of the battery 106, thus obtaining a new value of v_limit.
For example, the nominal value of the inversion speed v_limit is equal to a value defined in a configuration stage or it is initialized with a default value. For example, the nominal value of the inversion speed v_limit is selected so that under controlled conditions, the nominal control logic alone makes it possible to maintain the state of charge of the battery 106, considering a closed path.
More specifically, the coefficient χ has a trend that is a function of the state of charge SoC of the battery 106 as shown in Figure 7a, in which the coefficient χ is equal to 1 for state of charge SoC values greater than the threshold value SoC°, whereas it decreases towards a minimum value (for example equal to 0.7) upon the decrease in the state of charge SoC until it reaches the minimum value for small and null values of the state of charge SoC. In this manner, the inversion speed value v_limit is reduced for small values of the state of charge SoC of the battery 106, whereas the inversion speed value v_limit remains substantially equal to the nominal value for high values of the state of charge SoC of the battery 106.
Moreover, in step 202, the minimum value i_rec,min is calculated as a function of the state of charge SoC of the battery 106, said minimum value i_rec,min corresponding to the maximum energy recovery when the pedal-thrust group has no traction and when the bicycle is not braking.
In particular, in step 202, the nominal value i_rec,min is scaled (that is, multiplied) by a coefficient ξ having values comprised between 0 and 1 as a function of the state of charge SoC of the battery 106, thus obtaining a new minimum value i_rec,min.
For example, the nominal value i_rec,min is equal to a value defined in a configuration stage or it is initialized with a predefined value. For example, the nominal value i_rec,min is selected so that under controlled conditions, the nominal control logic alone makes it possible to maintain the state of charge of the battery 106, considering a closed path.
More specifically, the coefficient ξ has a trend that is a function of the state of charge SoC of the battery 106 as shown in Figure 7b, in which the coefficient ξ is equal to a minimum value (for example equal to 0.4) for state of charge SoC values greater than the threshold value SoC°, whereas it increases towards the value of 1 upon the decrease in the state of charge SoC until it reaches the value of 1 for small and null values of the state of charge SoC. In this manner, the value i_rec,min increases for small values of the state of charge Soc of the battery 106, whereas the value i_rec,min decreases for high values of the state of charge SoC of the battery 106.
Step 202 is followed by step 203, in which for a plurality of first states associated with the bicycle 100 during its movement, a plurality of trends of a first portion i°_cyclist of the motor nominal command signal I°_motor are calculated, as a function of the calculated values (that is, scaled) of the inversion speed v_limit and of the minimum value i_rec,min.
Said plurality of first states associated with the bicycle 100 are defined in advance (for example, they are predefined or they are configured by the cyclist) and for example they are the "Boost", "Traction", "Braking" and "No Traction" states illustrated previously in the description of the first state machine in Figure 3.
More specifically, in step 203 the trends of the first portion i°_cyclist (of the motor nominal command signal I°_motor) are calculated for the "Boost", "Traction", "Braking" and "No Traction" states shown in Figures 4a, 4b, 4c and 4d, respectively.
Step 203 is followed by step 204, in which the first current state associated with the bicycle 100 during its movement is identified, as a function of the value of a signal representative of the angular speed ω_wheel of the wheel 102 and of the value of a signal representative of the angular speed ω_free-wheel of the free-wheel mechanism 105 associated with the wheel 102.
Moreover, in step 204, the current trend of the first portion i°_cyclist associated with the identified first current state of the bicycle 100 is selected from the plurality of trends of the first portion I°_cyciist of the motor nominal command signal I°_motor.
In conclusion, in step 204, for the selected trend of the first portion i°_cyclist, the current value of the first portion i°_cyclist of the motor nominal command signal I°_motor is calculated as a function of the current value of the speed v of the bicycle. The speed v of the bicycle 100 is calculated for example as a function of the current value of the angular speed ω_wheel of the wheel 102 by means of the relation v = ω_wheel*R, in which R is the radius of the wheel 102.
For example:

in step 204, it is identified that the bicycle 100 is in the first "Traction" state, then the trend of the first portion i°_cyclist shown in Figure 4b is selected and the value i°_cyclist is calculated for the latter as a function of the current value of the speed v of the bicycle 100; or
in step 204, it is identified that the bicycle 100 is in the first "Boost" state, then the trend of the first portion i°_cyclist shown in Figure 4a is selected and the value i°_cyclist is calculated for the latter as a function of the current value of the speed v of the bicycle 100; or
in step 204, it is identified that the bicycle 100 is in the first "No Traction" state, then the trend of the first portion i°_cyclist shown in Figure 4d is selected and the value i°_cyclist is calculated for the latter as a function of the current value of the speed v of the bicycle 100; or
in step 204 it is identified that the bicycle 100 is in the first "Braking" state, then the trend of the first portion i°_cyclist shown in Figure 4c is selected and the value i°_cyclist is calculated for the latter as a function of the current value of the speed v of the bicycle 100.

Step 204 is followed by step 205, in which a second current state, out of a plurality of second states associated with the bicycle 100 during its movement, is identified, as a function of the value of a signal representative of the slope ϑ̃ of the road on which the bicycle 100 is travelling.
Moreover, in step 205, the current trend of the second portion i°_slope associated with the identified second state of the bicycle 100 is selected from a plurality of trends of a second portion i°_slope of the motor nominal command signal I°_motor.
Said plurality of second states are for example the "Downhill", "Flat" and "Uphill" states illustrated previously in the description of the second state machine in Figure 3.
Step 205 is followed by step 206, in which, for the selected trend of the second portion i°_slope, the current value of the second portion i°_slope of the motor nominal command signal I°_motor is calculated as a function of the current value of the slope ϑ̃ of the road.
For example:

in step 206 it is identified that the bicycle 100 is in the second "Uphill" state, then the trend of the second portion i°_slope shown in Figure 4e is selected and the value i°_slope is calculated for the latter as a function of the current value of the slope ϑ̃ of the road; or
in step 206 it is identified that the bicycle 100 is in the second "Downhill" state, then the trend of the second portion i°_slope shown in Figure 4f is selected and the value i°_slope is calculated for the latter as a function of the current value of the slope ϑ̃ of the road.

Step 206 is followed by step 207, in which the motor nominal command signal I°_motor is calculated as the sum of the first portion i°_cyclist and the second portion i°_slope.
Note that steps 205 and 206 are optional, that is, the cycle can proceed directly from step 204 to step 207. In this case, the motor nominal command signal I°_motor only comprises the contribution of the first portion i°_cyclist.
Step 207 is followed by step 208, in which it is verified whether the calculated value of the motor nominal command signal I°_motor is greater than 0:

in the positive case (that is I°_motor>0), step 208 is followed by step 209;
in the negative case (that is I°_motor<0), step 208 is followed by step 210.

In step 209, the current value of the motor corrected command signal I°_{motor, corr} is calculated as a function of the state of charge SoC of the battery 106.
In particular, in step 209 the motor corrected command signal I°_{motor, corr} is scaled (that is, multiplied) by a coefficient µ⁺ having values between 0 and 1 as a function of the state of charge SoC of the battery 106, thus obtaining a new value of the motor corrected command Signal I°_{motor, corr}.
More specifically, the coefficient µ⁺ has a trend that is a function of the state of charge SoC of the battery 106, as shown in Figure 6a, in which the coefficient µ⁺ is equal to 1 for state of charge SoC values greater than the threshold value SoC°, whereas it decreases towards the value of 0 for values lower than the threshold value SoC° until it becomes null for small and null values of the state of charge SoC. In this manner, the assistance provided to the cyclist is reduced in the case of a low state of charge SoC of the battery 106, until it is eliminated so as to prevent the battery 106 from discharging completely.
In step 210, the current value of the motor corrected command signal I°_{motor, corr} is calculated as a function of the state of charge SoC of the battery 106.
In particular, in step 210 the motor corrected command signal I°_{motor, corr} is scaled (that is, multiplied) by a coefficient µ^- having values comprised between 0 and 1 as a function of the state of charge SoC of the battery 106, thus obtaining a new value of the motor corrected command signal I°_{motor, corr}.
More specifically, the coefficient µ^- has a trend that is a function of the state of charge SoC of the battery 106, as shown in Figure 6b, in which the coefficient µ⁺ is equal to 1 for state of charge SoC values lower than the threshold value SoC°, whereas it decreases towards the value of 0 for values greater than the threshold value SoC° until it reaches the null value at the full charge value. In this manner, recharging is reduced in the case of a high state of charge of the battery 106, thereby avoiding useless fatigue of the cyclist.
From steps 209 and 210, the cycle proceeds to step 211 in which the value of a motor limit command signal I°_motor,lim I° is calculated as a function of the value of the motor corrected command signal I°_motor,corr and by taking into consideration one or more of the following values: the maximum value Vcell_max of the voltage across the battery 106, the minimum value Vcell_min of the voltage across the battery 106, the current value of the speed v of the bicycle 100, and the current value of the temperature of the electric motor 101.
In particular, calculation of the motor limit command signal I°_motor,lim is carried out by scaling (that is, by multiplying) the motor limit command signal I°_motor,lim by one or more of the coefficients η, ϑ, σ illustrated previously in the description of the saturation modules 8', 8", 8''' shown in Figure 2.
Step 211 is followed by step 212 in which the current value of a motor filtered command signal I°_motor,filtr is calculated as a function of the current value of the motor limit command signal I°_motor,lim.
Note that the presence of step 211 is optional, that is, it is possible to pass directly from steps 209, 210 to step 212.In this case, the current value of the motor filtered command signal I°_motor,filtr coincides with the calculated current value of the motor corrected command signal I°_motor,corr.
Step 212 is followed by step 213, in which the current value of a motor reference command signal I°_ref is calculated as a function of the current value of the motor filtered command signal I°_motor,filtr and as a function of the detection of a failure of the motor 101.
Step 213 is followed by step 214, in which the electric motor 101 is driven using the calculated current value of the motor reference command signal I°_ref .
The cycle returns to step 202 from step 214 and then a second cycle is performed in which steps 202-214 are repeated as illustrated above.
In particular, during the second cycle, the value of the inversion speed v_limit is recalculated in step 202, as a function of the current value of the state of charge SoC of the battery 106, for example by scaling the calculated value of the inversion speed v_limit in the first cycle with the coefficient χ and obtaining a new value of the inversion speed v_limit. Likewise, during the second cycle the minimum value i_rec,min is recalculated in step 202, as a function of the current state of charge SoC of the battery 106, for example by scaling the minimum value i_rec,min calculated in the first cycle with the coefficient ξ and obtaining a new minimum value i_rec,min.
As a result, during the second cycle the plurality of trends of the first portion i°_cyclist of the motor nominal command signal I°_motor are recalculated in step 203, as a function of the recalculated values of the inversion speed v_limit and the minimum value i_rec,min.
Moreover, during the second cycle the current value of the motor corrected command signal I°_{motor, corr} is recalculated in steps 209 and 210, as a function of the current value of the state of charge SoC of the battery 106, for example by scaling the value calculated in the first cycle with the coefficient µ⁺ or with the coefficient µ^-.
Note that the presence of step 213 is optional, that is, it is possible to pass directly from step 212 to step 214. In this case, the current value of the motor reference command signal I°_ref coincides with the calculated current value of the motor filtered command signal I°_motor,filtr.
Likewise, the presence of steps 211, 212 and 213 is optional. In this case, the current value of the motor reference command signal I°_ref coincides with the current value of the motor corrected command Signal I°_motor,corr.
It is also an object of the present invention an electronic control system 1 to drive an electric motor 101 of a electrically pedal-assisted bicycle 100 by means of a rechargeable battery 106, wherein the electric motor is configured to operate as a motor supplied by the battery 106 or as an electric generator for recharging the battery 106.
The electronic control system 1 comprises a processing unit that implements the nominal control module 2 and the adaptive control module 3, both of which are described hereinabove, by means of a suitable software code and/or hardware components.
The processing unit is for example a microprocessor, a microcontroller, a programmable logic device or a dedicated circuit.
The electronic control system 1 further comprises a measurement circuit to measure the state of charge SoC of the battery 106 and it is electrically connected to the battery 106 and to the processing unit.
The electronic control system 1 further comprises a current management circuit, which is electrically connected to the battery 106 and to the electric motor 101 and it is electrically connected to the processing unit. The current management circuit has the function of controlling the direction of the current between the battery 106 and the electric motor 101, so that the latter can operate as a motor or as an electric generator.
The processing unit, the measurement circuit for measuring the state of charge SoC and the current management circuit are positioned inside the hub of the rear wheel 102 of the bicycle 100.
The processing unit is configured to:

calculate the value of a inversion speed v_limit as a function of the state of charge SoC of the battery 106, said inversion speed indicating the speed of the bicycle beneath which the electric motor operates as a motor to supply assistance to the pedal-thrust and above which the motor operates as a generator when the moving bicycle is in a condition of traction in which the speed of a wheel 102 of the bicycle is substantially equal to the speed of the free-wheel mechanism 105;
calculate a minimum value i_rec,min as a function of the state of charge SoC of the battery 106, said minimum value i_rec,min corresponding to the maximum energy recovery when the pedal-thrust group has no traction and when the bicycle is not braking;
calculate, for a plurality of first states associated with the bicycle 100 during its movement, a plurality of trends of a first portion i°_cyclist of a motor nominal command signal I°_motor, as a function of the calculated values of the inversion speed v_limit and of the minimum value i_rec,min;
identify the first current state associated with the bicycle 100 during its movement, as a function of the value of a signal representative of an angular speed ω_wheel of the wheel and of the value of a signal representative of an angular speed ω_free-wheel of the free-wheel mechanism 105.
select, from the plurality of trends of the first portion i°_cyclist of the motor nominal command signal I°_motor, the current trend of the first portion i°_cyclist, said current trend being associated with the identified first current state;
calculate, for the selected trend of the first portion i°_cyclist, the current value of the first portion i°_cyclist of the motor nominal command signal I°_motor, as a function of the current value of the bicycle speed v;
calculate the current value of a motor corrected command signal I°_{motor, corr} as a function of the first portion i°_cyclist and the state of charge SoC of the battery 106;
drive the electric motor 101, using the calculated current value of the motor corrected command signal I°_{motor, corr};
further repeat the calculation of the value of the inversion speed v_limit, the calculation of the minimum value i_rec,min, the calculation of the plurality of trends of the first portion i°_cyclist of the motor nominal command signal i°_cyclist, the identification of the first current state associated with the bicycle 100 during its movement, the selection of the current trend of the first portion i°_cyclist associated with the identified first current state, the calculation of the current value of the first portion i°_cyclist of the motor nominal command signal I°_motor, calculation of the current value of the motor corrected command signal I°_{motor, corr}, and the driving of the electric motor 101 using the calculated current value of the motor corrected command signal I°_{motor, corr}.

Preferably, the processing unit is configured to calculate the inversion speed by scaling the value of the inversion speed v_limit with a first coefficient χ that depends on the state of charge of the battery, wherein said first coefficient χ is equal to one for values of the state of charge SoC that are greater than a threshold value SoC° and it decreases towards a minimum value upon the decrease in the state of charge SoC until it reaches the minimum value for small and null values of the state of charge;moreover the processing unit is configured to calculate the minimum value i_rec,min by scaling the minimum value i_rec,min with a second coefficient ξ that depends on the state of charge of the battery, wherein said second coefficient ξ is equal to a minimum value for values of the state of charge SoC that are greater than the threshold value SoC° and it increases towards the value of one upon the decrease in the state of charge until it reaches the value of one for small and null values of the state of charge.
Preferably, said plurality of first states comprises at least two of the following states:

▪ Boost: it corresponds to a standing start or abrupt acceleration during the movement phase of the bicycle;
▪ No Traction: it corresponds to a condition in which, when the bicycle is moving, the speed of the free-wheel mechanism is lower than the speed of the wheel;
▪ Traction: corresponding to a condition in which the speed of the free-wheel mechanism is substantially equal to the speed of the bicycle wheel;
▪ Braking: it corresponds to a braking condition.

Preferably, the processing unit is configured to:

identify the Traction state;
select the trend of the first portion associated with the Traction state, said trend comprising:
- ▪ a first portion comprised between a null value of the speed of the bicycle and a defined value v_curr,max, wherein the first portion i°_cyclist of the motor nominal command signal gradually increases from the null value to a maximum value i_boost,max;
- ▪ a second portion comprised between said defined value v_curr,max of the speed of the bicycle and the inversion speed value v_limit, wherein the second portion i°_cyclist of the motor nominal command signal gradually decreases until it reaches the null value;
- ▪ a third portion comprised between the inversion speed value v_limit and a maximum speed value v_rech,max, wherein the third portion i°_cyclist of the motor nominal command signal is negative until it reaches said minimum value i_rec,min;
a fourth portion greater than the maximum speed value v_rech,max, wherein the fourth portion i°_cyclist of the motor nominal command signal is substantially equal to said minimum value i_rec,min.

Preferably, the processing unit is configured to calculate the current value of the motor corrected command signal I°_{motor, corr}:

in case wherein the value of the first portion i°_cyclist of the motor nominal command signal is positive, by scaling the first portion i°_cyclist of the nominal command signal for the motor with a third coefficient µ⁺ that depends on the battery state of charge, wherein the third coefficient µ⁺ is equal to one for values of the state of charge that are greater than the threshold value SoC°, whereas it decreases towards the null value for values lower than the threshold value SoC° until it becomes null for small and null values of the state of charge;
in case wherein the value of the first portion i°_cyclist of the motor nominal command signal is negative, by scaling the first portion i°_cyclist of the motor nominal command signal with a fourth coefficient µ^- that depends on the battery state of charge, wherein the fourth coefficient µ^- is equal to one for values of the state of charge that are lower than the threshold value SoC°, whereas it decreases towards the null value for values greater than the threshold value SoC° until it reaches the null value at the full charge value.

It is also an object of the present invention an electrically pedal-assisted bicycle 100, comprising:

a rechargeable battery 106;
an electric motor 101 configured to operate as a motor supplied by the battery 106 or as an electric generator for recharging the battery 106;
the electronic control system 1 as illustrated hereinabove.

Claims

Adaptive system (1) to control a pedal-assisted bicycle (100) comprising an electric motor (101) configured to operate as a motor and as a generator associated with a wheel (102) of the bicycle (100), a rechargeable battery (106) having a power exchange relationship with the electric motor (101), a pedal-thrust group (103) to be pedaled by a cyclist, a transmission (104) operatively interposed between the pedal-thrust group (103) and a wheel (102) of the bicycle comprising a free-wheel mechanism (105), the system comprising:
- a sensor configured to generate a signal representative of an angular speed (ω_wheel) of a wheel (102) of the bicycle;

- a sensor configured to generate a signal representative of an angular speed (ω_free-wheel) of the free-wheel mechanism (105);

- a sensor configured to generate a signal representative of a state of charge (SoC) of the battery (106);

- a nominal control module (2) configured to generate a motor nominal command signal (I°_motor) based at least on said signals representative of the angular speed (ω_wheel) of the wheel (102) and of the angular speed (ω_free-wheel) of the free-wheel mechanism (105), wherein said motor nominal command signal (I°_motor) or a portion (i°_cyclist) thereof is defined by an inversion speed (v_limit) of the bicycle beneath which the motor (101) supplies an assistance to the pedal-thrust and above which the motor (101) operates as a generator when the moving bicycle is in a traction condition in which the speed of the wheel (102) of the bicycle is substantially equal to the speed of the free-wheel mechanism (105), and wherein said motor nominal command signal (I°_motor) or a portion (i°_cyclist) thereof is further defined by a maximum energy recovery value (i_rec,min) when the pedal-thrust group has no traction and when the bicycle is not braking;

- an adaptive control module (3) configured to:
• generate a motor corrected command signal (I°_motor,corr) determined from the motor nominal command signal (I°_motor) corrected based on the signal representative of the state of charge (SoC) of the battery (106);
wherein the adaptive control system (1) is further configured to supply to the motor (101) a reference command signal (I°_ref) determined based on said motor corrected command signal (I°_motor,corr) characterized in that the adaptive control module (1320,1323,1325) is further configured to modify said inversion speed and said maximum energy recovery value (Tc) of the motor nominal command signal or of a portion thereof based on the signal representative of the state of charge (SoC).
Adaptive system according to claim 1, wherein the adaptive control module (3) comprises a module (10) for correcting the parameters of the nominal control module (2), which is configured to modify said inversion speed (v_limit) and said maximum energy recovery value (i_rec,min) of the motor nominal command signal (I°_motor) or of a portion (i°_cyclist) thereof based on the signal representative of the state of charge (SoC), so that, as the state of charge decreases, the inversion speed (v_limit) decreases and the maximum energy recovery value (i_rec,min) of the motor nominal command signal (I°_motor) or of a portion (i°_cyclist) thereof increases in absolute value,
and as the state of charge increases, the inversion speed (v_limit) increases and the maximum energy recovery value (i_rec,min) of the motor nominal command signal (I°_motor) or of a portion (i°_cyclist) thereof reduces in absolute value.
Adaptive system according to claim 1 or 2, wherein the adaptive control module (3) comprises a module (9) for correcting the nominal command signal configured to modulate the motor nominal command signal (I°_motor) based on the signal representative of the state of charge (SoC) of the battery, such that the motor nominal command signal (I°_motor), when positive, decreases as the state of charge of the battery decreases, and, when negative, decreases in absolute value as the state of charge of the battery increases.
Adaptive system (1) according to claim 1, wherein the nominal control module (2) comprises a first finite state machine (6) configured to output the motor nominal command signal (I°_motor) or a first portion (i°_cyclist) of the motor nominal command signal (I°_motor), determined based on a state calculated as a function of at least the signal representative of the wheel angular speed (ω_wheel) and on the signal representative of the angular speed (ω_free-wheel) of the free-wheel mechanism,
wherein the first finite state machine (6) is configured to detect at least two of the following states:
- BOOST state: it corresponds to a standing start or to an abrupt acceleration during the movement phase of the bicycle, the state having finite duratione determinable based on the number of pedal-thrust turns or after exceeding a predefined threshold speed of the bicycle;

- NO TRACTION state: it corresponds to a condition wherin, when the bicycle is moving, the speed of the free-wheel mechanism is less than the speed of the wheel;

- TRACTION state: it corresponds to a condition wherein the speed of the free-wheel mechanism is equal, unless for a tolerance, to the speed of the bicycle wheel;

- BRAKING state: it corresponds to a braking condition of the bicycle,
wherein said bicycle inversion speed (v_limit) and said maximum energy recovery value (i_rec,min) without braking define the motor nominal command signal (I°_motor) or the first portion (i°_cyclist) thereof in the TRACTION state.
Adaptive system (1) according to any one of the previous claims, further comprising a sensor configured to generate a signal representative of the slope (ϑ̃) of the bicycle route,
wherein the nominal control module (2) further comprises a second finite state machine (7) configured to generate a second portion (i°_slope) of the motor nominal command signal (I°_motor), said second portion (i°_slope) being determined based on a state calculated as a function of the signal representative of the slope (ϑ̃),
wherein the motor nominal command signal (I°_motor) is equal to the sum of the first portion (i°_cyclist) generated by the first finite state machine (6) and of the second portion (i°_slope) generated by the second finite state machine (7),
and wherein the second finite state machine (7) is configured to detect at least two of the following states:
- DOWNHILL: it corresponds to a condition in which the bicycle is moving along a downhill route;

- FLAT: it corresponds to a condition in which the bicycle is moving along a substantially flat route;

- UPHILL: it corresponds to a condition in which the bicycle is moving along an uphill route.
Adaptive system (1) according to any one of the previous claims, further comprising one or more saturation modules (8', 8", 8''') of the motor corrected command signal (I°_motor,corr), configured to generate a motor limit command signal (I°_motor,lim), obtained from the motor corrected command signal (I°_motor,corr) reduced in absolute value based on detected operating parameters of the electric motor (101) and/or of the battery (106),
wherein said one or more saturation modules (8', 8", 8''') of the motor corrected command signal (I°_motor,corr) comprise:
- a first saturation module (8') configured to reduce, in absolute value, the motor corrected command signal (I°_motor,corr) such that the voltage of the battery (106) is kept within a range comprised between a maximum limit value (Vcell_max) and a minimum limit value (Vcell_min);

- a second saturation module (8") configured to reduce, in absolute value, the motor corrected command signal (I°_motor,corr) based on the signal representative of the angular speed (ω_wheel) of the wheel (102), the system further comprising a sensor configured to generate a signal representative of the temperature (T) of the motor, wherein said one or more saturation modules (8', 8", 8''') of the motor corrected command signal (I°_motor,corr) comprise a third saturation module (8''') configured to reduce the motor corrected command signal (I°_motor,corr), when the latter signal is positive, based on said signal representative of the temperature (T) of the motor (101).
Adaptive system (1) according to any one of the previous claims, comprising a filter (4) configured to filter the motor corrected command signal (I°_motor,corr) or the motor limit command signal (I°_motor,lim) and output a motor filtered command signal (I°_motor,filtr), wherein the reference command signal (I°_ref) coincides with said motor filtered command signal (I°_motor,filtr).
Adaptive system (1) according to any one of the previous claims, comprising a failure detecting module (5) configured to deactivate the motor (101) or to modulate the motor reference command signal (I°_ref) in the presence of detected failures in the system (1).
Electrically pedal-assisted bicycle (100), the bicycle comprising:
- a rechargeable battery (106);

- an electric motor (101) configured to operate as a motor supplied by the battery (106) or as an electric generator for recharging the battery (106);

- an adaptive system (1) according to any of the previous claims.
Method (200) for driving an electric motor (101) of a electrically pedal-assisted bicycle (100) by means of a rechargeable battery (106), the electric motor being configured to operate as a motor supplied by the battery or as an electric generator for recharging the battery, the bicycle comprising a free-wheel mechanism (105) associated with a wheel (102) of the bicycle, the method comprising the steps of:
a1) calculating (202) the value of a inversion speed (v_limit) as a function of a state of charge (SoC) of the battery (106), said inversion speed indicating the bicycle speed beneath which the electric motor operates as a motor to supply assistance to the pedal-thrust and above which the motor operates as a generator, when the moving bicycle is in a traction condition in which the speed of a wheel (102) of the bicycle is substantially equal to the speed of a free-wheel mechanism (105);

a2) calculating (202), as a function of the state of charge (SoC) of the battery (106), a minimum value (i_rec,min) corresponding to the maximum energy recovery when the pedal-thrust group has no traction and when the bicycle is not braking;

b) calculating (203), for a plurality of first states associated with the bicycle (100) during its movement, a plurality of trends of a first portion (i°_cyclist) of a motor nominal command signal (I°_motor), as a function of the calculated values of the inversion speed (v_limit) and of the minimum value (i_rec,min) ;

c1) identifying (204), as a function of the value of an angular speed (ω_wheel) of the wheel and of an angular speed (ω_free-wheel) of the free-wheel mechanism (105), the first current state associated with the bicycle (100) during its movement;

c2) selecting (204), out of the plurality of trends of the first portion (i°_cyclist) of the motor nominal command signal (I°_motor), the current trend of the first portion i°_cyclist associated with the identified first current state;

c3) calculating (204), for the selected trend of the first portion (i°_cyclist), the current value of the first portion (i°_cyclist) of the motor nominal command signal (I°_motor), as a function of the current value of the bicycle speed (v);

d) calculating (208, 209, 210) the current value of a motor corrected command signal (I°_{motor, corr}) as a function of the first portion (i°_cyclist) and of the state of charge (SoC) of the battery;

e) driving ((214) the electric motor (101) using the calculated current value of the motor corrected command signal (I°_{motor, corr}) ;

f) further repeating steps a1), a2), b), c1), c2), c3), d), e).
Method according to claim 10, wherein in step a1) the inversion speed is calculated by scaling the inversion speed value (v_limit) with a first coefficient (χ) that depends on state of charge of the battery, wherein the first coefficient (χ) is equal to one for values of the state of charge (SoC) that are greater than a threshold value (SoC°) and decreases towards a minimum value as the state of charge (SoC) decreases until it reaches the minimum value for small and null values of the state of charge,
and wherein in step a2) the minimum value (i_rec,min) is calculated by scaling the minimum value (i_rec,min) with a second coefficient (ξ) that depends on the state of charge of the battery, wherein the second coefficient (ξ) is equal to a minimum value for values of the state of charge (SoC) that are greater than the threshold value (SoC°) and it increases towards the value one as the state of charge decreases until it reaches the value of one for small and null values of the state of charge.
Method according to claims 10 or 11, wherein in step b) said plurality of first states comprises at least two of the following states:
▪ Boost: it corresponds to a standing start or abrupt acceleration during the movement phase of the bicycle;

▪ No traction: it corresponds to a condition in which, when the bicycle is moving, the speed of the free-wheel mechanism is less than the speed of the wheel;

▪ Traction: it corresponds to a condition in which the speed of the free-wheel mechanism is substantially equal to the speed of the bicycle wheel;

▪ Braking: it corresponds to a braking condition.
Method according to claim 12, wherein:
- step c1) comprises identifying the Traction state;

- step c2) comprises selecting the trend of a first portion associated with the Traction state, said trend comprising:
▪ a first portion comprised between a null value of the speed of the bicycle and a defined value (v_curr,max), wherein the first portion (i°_cyclist) of the motor nominal command signal gradually increases from the null value to a maximum value (i_boost,max);

▪ a second portion comprised between said defined value (v_curr,max) of the speed of the bicycle and the inversion speed value (v_limit), wherein the first portion (i°_cyclist) of the motor nominal command signal gradually decreases until it reaches the null value;

▪ a third portion comprised between the inversion speed value (v_limit) and a maximum speed value (v_rech,max), wherein the third portion (i°_cyclist) of the motor nominal command signal is negative until it reaches said minimum value (i_rec,min);

▪ a fourth portion greater than the maximum speed value (v_rech,max), wherein the fourth portion (i°_cyclist) of the motor nominal command signal is substantially equal to said minimum value (i_rec,min).
Method according to any of claims from 10 to 13, wherein in step d) the current value of the motor corrected command signal (I°_{motor, corr}) is calculated:
- in case wherein the value of the first portion (i°_cyclist) of the motor nominal command signal is positive, by scaling the first portion (i°_cyclist) of the motor nominal command signal with a third coefficient (µ⁺) that depends on the state of charge of the battery, wherein the third coefficient (µ⁺) is equal to one for values of the state of charge that are greater than the threshold value (SoC°), whereas it decreases towards the null value for values lower than the threshold value (SoC°) until it becomes null for small and null values of the state of charge;

- in case wherein the value of the first portion (i°_cyclist) of the motor nominal command signal is negative, by scaling the first portion (i°_cyclist) of the motor nominal command signal with a fourth coefficient (µ^-) that depends on the battery state of charge, wherein the fourth coefficient (µ^-) is equal to one for values of the state of charge that are lower than the threshold value (SoC°), whereas it decreases towards the null value for values greater than the threshold value (SoC°) until it reaches the null value at the full charge value.
Computer program comprising software code portions adapted to perform the steps of the method according to any of claims from 10 to 14, when said program is running on at least one computer.